<div class="header-navigator"></div><div class='markdown-body'><pre class="language-bash"><code>
&lt;factor&gt;::= &lt;base&gt; &lt;quantifier&gt;?

&lt;base&gt;  ::= &lt;char&gt;
          | &#x27;\123&#x27; &lt;c[h](123)ar&gt;
          | &#x27;(&#x27; &lt;regex&gt; &#x27;)&#x27;</code></pre><p>1<a href="123" target="_blank">2</a>3</p></div>